Sulfonated iminodialkanoic acids formed from an iminodialkylnitrile and a sultone and methods for use thereof

ABSTRACT

Complexation of metal ions using chelating agents within a subterranean formation can often be desirable, such as to temper the formation of metal-containing precipitates. However, many chelating agents are produced commercially in an alkali metal salt form that may not be entirely suitable for use downhole, particularly in subterranean formations containing a siliceous material. The working pH range of some types of chelating agents may also be limiting. Treatment fluids comprising an aqueous carrier fluid having an acidic pH, a sulfonated iminodialkanoic acid, and ammonium ions may at least partially address downhole precipitation issues, while providing further advantages as well. Methods for forming sulfonated iminodialkanoic acids can comprise reacting an iminodialkylnitrile with a sultone under acidic conditions to form a fluid comprising a sulfonated iminodialkanoic acid and ammonium ions.

BACKGROUND

The present disclosure generally relates to complexation of metal ionsand, more specifically, to dissolution of minerals, chelating agentssuitable for use in conjunction with various subterranean treatmentoperations, and methods for synthesizing such chelating agents.

Treatment fluids can be used in a variety of subterranean treatmentoperations. Such treatment operations can include, without limitation,drilling operations, stimulation operations, production operations,remediation operations, sand control treatments, and the like. As usedherein, the terms “treat,” “treatment,” “treating,” and grammaticalequivalents thereof refer to any subterranean operation that uses afluid in conjunction with achieving a desired function and/or for adesired purpose. Use of these terms does not imply any particular actionby the treatment fluid or a component thereof, unless otherwisespecified herein. More specific examples of illustrative treatmentoperations can include, for example, drilling operations, fracturingoperations, gravel packing operations, acidizing operations, scaledissolution and removal operations, sand control operations,consolidation operations, and the like.

Acidic treatment fluids are frequently utilized in the course ofconducting various subterranean treatment operations. Illustrative usesof acidic treatment fluids during subterranean treatment operationsinclude, for example, matrix acidizing of siliceous and/or non-siliceousformations, scale dissolution and removal processes, gel breaking, acidfracturing, and the like.

Acidizing operations may be performed to stimulate a subterraneanformation and increase production of a hydrocarbon resource therefrom.During an acidizing operation, an acid-reactive material in thesubterranean formation can be at least partially dissolved by one ormore acids to expand existing flow pathways in the subterraneanformation, to create new flow pathways in the subterranean formation,and/or to remove acid-soluble scale in the subterranean formation.Acidizing a subterranean formation's matrix can be particularlyeffective for stimulating production.

The material being reacted with an acidizing fluid can significantlydictate how an acidizing operation is performed. When acidizing anon-siliceous substance, such as a carbonate material, mineral acids,such as hydrochloric acid, may often be sufficient to affectdissolution. Organic acids may be used in a similar manner tohydrochloric acid when dissolving a non-siliceous substance, especiallyat temperatures exceeding about 180° C. Siliceous materials, incontrast, are only readily dissolvable using hydrofluoric acid,optionally in combination with other acids to maintain a low pHenvironment. As used herein, the term “siliceous” refers to a substancehaving the characteristics of silica, including silicates and/oraluminosilicates. Illustrative siliceous materials can include, forexample, silica, silicates, aluminosilicates, and any combinationthereof, optionally in further combination with a non-siliceoussubstance, such as a carbonate material. Most sandstone formations, forexample, contain about 40% to about 98% sand quartz particles (i.e.,silica), bonded together by various amounts of cementing materials,which may be siliceous in nature (e.g., aluminosilicates or othersilicates) or non-siliceous in nature (e.g., carbonates, such ascalcite).

Carbonate formations contain minerals that comprise a carbonate anion.Calcite (calcium carbonate), dolomite (calcium magnesium carbonate), andsiderite (iron carbonate) represent illustrative examples. Whenacidizing a carbonate formation, acidity of the treatment fluid alonecan often be sufficient to solubilize the carbonate material byconverting the carbonate anion into carbon dioxide and leaching a metalion into the treatment fluid. As the concentration of dissolved metalions rises, particularly at higher pH values upon spending of the acid,the solubility limit of the metal ions may be exceeded and precipitationof scale may occur.

Siliceous formations can include minerals such as, for example,zeolites, clays and feldspars. As indicated above, siliceous formationsare usually acidized with hydrofluoric acid, optionally in combinationwith another acid, in order to react the siliceous minerals and affecttheir dissolution. Dissolved silicon species can be particularly pronetoward undergoing secondary reactions with alkali metal ions to formhighly damaging alkali metal silicate precipitates. Co-presentnon-siliceous minerals, such as carbonate minerals, may be concurrentlydissolved while acidizing a siliceous material and lead to furtherprecipitation issues.

Calcium ions and other alkaline earth metal ions can be particularlyproblematic when acidizing either siliceous or non-siliceous formations.As indicated above, the solubility limit of the metal ions may bequickly exceeded and deposition of scale may occur upon spending of anacid. In the case of siliceous formations acidized with hydrofluoricacid, calcium ions liberated from a co-present carbonate material canreact readily with free fluoride ions to form highly insoluble calciumfluoride. Other metal ions can prove similarly problematic in thisregard, either by forming an insoluble reaction product withhydrofluoric acid or by themselves upon forming an insoluble materialunder the particular conditions present in a wellbore. Calcium fluorideand other types of scale formed from metal ions can be highly damagingto subterranean formations, possibly even more so than if the initialacidizing operation had not been performed in the first place.

One approach that has been used to address the issues associated withdissolved metal ions is to employ chelating agents, which can sequesterthe metal ions in a more soluble and less reactive form of ametal-ligand complex. As used herein, the terms “complex,” “complexing,”“complexation” and other variants thereof refer to the formation of ametal-ligand bond without reference to the mode of bonding. Althoughcomplexation of metal ions may involve a chelation process, complexationis not deemed to be limited in this manner. Once bound in a metal-ligandcomplex, the metal ions may have a significantly decreased propensity toundergo a further reaction to form scale.

There are difficulties associated with chelation strategies, however. Atlow pH values, the carboxylic acid groups of many chelating agents maybe substantially protonated, a form that can be ineffective forpromoting metal ion complexation. This issue can significantly limit theworking pH range over which an acidizing operation may take place,potentially limiting the acidizing operation's speed and effectiveness(i.e., by working at higher pH values). In addition, many chelatingagents are commercially supplied in their alkali metal salt forms, whichcan be especially problematic for siliceous formations due to theprecipitation issues noted above. Conversion of the alkali metal saltform of a chelating agent into the free acid form or an alternative saltform can often be problematic and/or expensive, particularly at thelarge scales needed to support subterranean treatment operations.Although numerous chelating agents are known, there are presently a verylimited number available in suitable form and in sufficient supply tosupport widespread downhole use. Provisions for working with the lessdesirable alkali metal salt forms of commodity chelating agentspresently may need to be made in order to facilitate their use insubterranean treatment operations.

BRIEF DESCRIPTION OF THE DRAWINGS

The following figures are included to illustrate certain aspects of thepresent disclosure and should not be viewed as exclusive embodiments.The subject matter disclosed is capable of considerable modifications,alterations, combinations, and equivalents in form and function, as willoccur to one having ordinary skill in the art and the benefit of thisdisclosure.

FIG. 1 shows an illustrative schematic of a system that can delivertreatment fluids of the present disclosure to a downhole location,according to one or more embodiments.

FIG. 2 shows a bar graph summarizing the amounts of CaCl₂ and NaOH addedto the chelant solution of Example 1 and the resulting pH values.

FIG. 3 shows a plot of differential pressure and permeability for acalcite core contacted with the chelant solution of Example 1 as afunction of time.

DETAILED DESCRIPTION

The present disclosure generally relates to complexation of metal ionsand, more specifically, to dissolution of minerals, chelating agentssuitable for use in conjunction with various subterranean treatmentoperations, and methods for synthesizing such chelating agents.

One or more illustrative embodiments incorporating the features of thepresent disclosure are presented herein. Not all features of a physicalimplementation are necessarily described or shown in this applicationfor the sake of clarity. It is to be understood that in the developmentof a physical implementation incorporating the embodiments of thepresent disclosure, numerous implementation-specific decisions may bemade to achieve the developer's goals, such as compliance withsystem-related, business-related, government-related and otherconstraints, which may vary by implementation and from time to time.While a developer's efforts might be time-consuming, such efforts wouldbe, nevertheless, a routine undertaking for one having ordinary skill inthe art and the benefit of this disclosure.

As discussed above, there are various issues associated with the use ofchelating agents in subterranean acidizing operations. In someinstances, the working pH range of the acidizing operation may belimited in order to maintain the chelating agent in an active form.Moreover, the as-supplied alkali metal salt form of many chelatingagents can be extremely problematic, particularly when used inconjunction with acidizing a subterranean formation containing asiliceous material. These issues frequently occur withaminopolycarboxylic acid chelating agents, which can otherwise bedesirable for use in subterranean treatment operations due to theirready complexation properties and environmentally friendly character inmany cases. Although the salt form of a chelating agent may be changedthrough acidification and ion exchange, these processes may be laborintensive, expensive and incompatible with commercial-scale production.Moreover, unless liberated alkali metal ions are removed from a solutionof the chelating agent, they can still end up in a formulated treatmentfluid and lead to the deleterious consequences noted above.

The present inventors discovered a new type of chelating agent thatovercomes several of the above issues and provides related advantages aswell. Namely, the inventors discovered that sulfonatedaminopolycarboxylic acids, more specifically sulfonated iminodialkanoicacids such as sulfonated iminodiacetic acids, can be especiallyadvantageous for use in acidizing operations. As used herein, the term“sulfonated” refers to the condition of a compound bearing a sulfonicacid group. Due to the presence of the very acidic sulfonic acid group,sulfonated iminodialkanoic acids can maintain high solubility levels andlow pH values in aqueous fluids, such as in aqueous acidizing fluids.

The inventors discovered various synthetic approaches through whichsulfonated iminodialkanoic acids may be readily obtained in a form thatis substantially free of alkali metal ions. Depending upon the chosensynthetic approach, the free acid form or an ammonium salt form of thesulfonated iminodialkanoic acids may be obtained. Such syntheticapproaches desirably avoid the use of base-promoted alkylation reactionsthat might otherwise introduce unwanted alkali metal ions into thesetypes of compounds.

In one synthetic approach, the inventors discovered that sulfonatediminodialkanoic acids may be synthesized in their free acid form underacidic conditions via a ring-opening process without alkali metal ionsbeing present. Specifically, an iminodialkanoic acid (e.g.,iminodiacetic acid) may be reacted in high yields with a sultone (e.g.,1,2-oxathietane 2,2-dioxide-ethane sultone, 1,2-oxathiolane2,2-dioxide-1,3-propane sultone, 1,2-oxathiane 2,2-dioxide-1,4-butanesultone, or various derivatives thereof) under acidic conditions toaccomplish the foregoing. The foregoing sultones are commerciallyavailable and can directly produce the free acid form of the sulfonatediminodialkanoic acid in a fluid concentrate that is substantially freeof alkali metal ions. The fluid concentrate may then be employeddirectly as a treatment fluid or undergo further dilution with a carrierfluid and/or other substances of interest to form a treatment fluid thatis substantially free of alkali metal ions. Sulfonated iminodialkanoicacids that are substantially free of alkali metal ions may beparticularly advantageous for acidizing a siliceous formation for thereasons discussed above.

In an improvement of the above-described ring-opening process, theinventors discovered that an iminodialkylnitrile can be substituted foran iminodialkanoic acid and undergo a reaction under similar conditionsto yield the same types of sulfonated iminodialkanoic acids. Under theacidic reaction conditions under which ring-opening occurs, the nitrilegroups also undergo hydrolysis in situ to form carboxylic acidfunctionalities. Unlike syntheses proceeding directly from animinodialkanoic acid, utilizing an iminodialkylnitrile as an acidprecursor allows ammonium ions to be produced in conjunction with thesulfonated iminodialkanoic acid. Ammonium ions can be a particularlydesirable ionic form for use in conjunction with acidizing operations,such as to provide clay stabilization effects, not to mention avoidingthe above-described formation of insoluble fluorine-containing compoundsderived from alkali metal ions. The ability to form ammonium ions insitu can obviate the need to modify a treatment fluid further tointroduce ammonium ions thereto. Iminodialkanoic acids and theircorresponding iminodialkylnitriles can also be fairly comparable interms of price, so the alternative synthetic approach providing in situammonium ion formation does not add significantly to cost burdens forforming a treatment fluid.

Regardless of how they are synthesized, sulfonated iminodialkanoic acidscan be particularly advantageous in acidizing operations, since they canbear sufficient acidity alone to dissolve an acid-reactive substance,such as a carbonate material, without another acid being present todecrease the pH. All of the acidic groups in sulfonated iminodialkanoicacids have pKa values under 6, with the most acidic group reachingnegative pK_(a) values, which can allow each acidic group to contributeto at least some degree in acid-promoted dissolution processes.Accordingly, due to their strong acidity, sulfonated iminodialkanoicacids can, in some instances, serve as a direct replacement for mineralacids and organic acids that are commonly used in acidizing operations.Optionally, a mineral acid or an organic acid can be used in combinationwith a sulfonated iminodialkanoic acid to further promote dissolution ofan acid-reactive substance. In particular embodiments, when used inconjunction with acidizing a subterranean formation containing asiliceous material, hydrofluoric acid or a hydrofluoric acid-generatingcompound can be used in combination with the sulfonated iminodialkanoicacids described herein. Alkali metal ions can be excluded from thetreatment fluids in either case, thereby allowing the advantages hereinto be realized.

Due to their ability to serve as an effective direct replacement for amineral acid or an organic acid, sulfonated iminodialkanoic acids mayalso be used as a secondary acid source in combination with anotherchelating agent. When combined with one or more other chelating agents,the sulfonated iminodialkanoic acid and the other chelating agents maypromote complexation of different metal ions and/or provideeffectiveness over differing pH ranges. For example, the sulfonatediminodialkanoic acid may complex metal ions at low pH values, and theother chelating agent(s) may promote complexation at higher pH values.

In spite of their strong acidity, sulfonated iminodialkanoic acids canadvantageously remain active for promoting metal ion complexation andlessen the likelihood of precipitate occurrence during subterraneantreatment operations. In particular, sulfonated iminodialkanoic acidscan maintain a high affinity for promoting complexation of calcium ions,other alkaline earth metal ions, and transition metal ions. Accordingly,sulfonated iminodialkanoic acids of the present disclosure can promotedissolution of metal-containing substances through both their acidityand their complexation properties.

Further, the sulfonated iminodialkanoic acids described herein may bereadily utilized in acidizing operations conducted in a carbonateformation or in a siliceous formation without significantly modifyingthe chelating agent's composition in a treatment fluid. In the case ofacidizing a siliceous formation, hydrofluoric acid or a hydrofluoricacid-generating compound can be present in a treatment fluid containingthe sulfonated iminodialkanoic acid or be introduced separately to asubterranean formation to promote dissolution of a siliceous materialtherein. As described above, ammonium ions in treatment fluids formedthrough in situ nitrile hydrolysis can be especially advantageous,particularly when clays and other siliceous materials are present andundergoing dissolution. The ability to use the sulfonatediminodialkanoic acids described herein in both types of acidizingoperations may significantly simplify these oilfield operations anddecrease their costs. As a further advantage, the sulfonatediminodialkanoic acids described herein may possess anti-scalingproperties, which can also be beneficial for conducting a treatmentoperation.

In various embodiments, the sulfonated iminodialkanoic acids describedherein may have the structure shown in Formula 1

wherein A₁ is a C1-C4 alkyl group, which may be substituted orunsubstituted and contain optional branching, and A₂ and A₃ areindependently C1-C10 alkyl groups, which may be the same or differentand may be substituted or unsubstituted and contain optional branching.In more particular embodiments, the sulfonated iminodialkanoic acidsdescribed herein may have the structure shown in Formula 2

wherein x is an integer ranging between 1 and 4, and y and z areindependently integers ranging between 1 and about 10, or between 1 andabout 3. In still more particular embodiments, the sulfonatediminodialkanoic acids described herein can be sulfonated iminodiaceticacids having the structure shown in Formula 3

in which x is defined as above. Sulfonated iminodiacetic acids in whichx is 3 can be formed readily from 1,3-propane sultone.

As indicated above, various synthetic approaches can be used to form thesulfonated iminodialkanoic acids of the present disclosure. Illustrativesynthetic approaches are discussed in more detail hereinafter. In thedescription that follows, the synthesis of sulfonated iminodialkanoicacids will be exemplified through the synthesis of sulfonatediminodiacetic acids. It is to be recognized, however, that othersulfonated iminodialkanoic acids may be produced by utilizing adifferent iminodialkanoic acid starting material or a precursor thereof.

In some embodiments, iminodiacetic acid or a salt thereof may bealkylated under basic conditions with a haloalkylsulfonic acid or a saltthereof, as shown in Reaction 1, wherein X is a halide or a halideequivalent, such as an alkylsulfonate or an arylsulfonate, and x isdefined as above.

In some instances, alkali metal ions introduced from the base can bedifficult to remove from the resulting sulfonated iminodiacetic acid. Inthe event that exclusion of alkali metal ions is desired, ammoniumhydroxide or other bases may be used to promote the alkylation process.Competing elimination reactions occurring at high pH can also beproblematic in this approach. Similar approaches starting fromiminodiacetonitrile can also be used to produce sulfonated iminodiaceticacids, with nitrile hydrolysis taking place in situ under basicconditions or under acidic conditions in a separate reaction step.Again, the introduction of unwanted alkali metal ions can beproblematic, and competing reactions can occur.

As indicated above, the inventors discovered alternative approaches forsynthesizing sulfonated iminodiacetic acids in their free acid form byreacting iminodiacetic acid with a sultone under acidic conditions. Suchapproaches can proceed with the substantial exclusion of problematicalkali metal ions. The general approach utilizing iminodiacetic acid anda sultone to form a sulfonated iminodiacetic acid is exemplified inReaction 2, wherein A is (CH₂)_(x) and x is 2, 3 or 4.

The particular example utilizing 1,3-propane sultone as the reactionpartner for iminodiacetic acid is shown in Reaction 3.

Similarly, Reaction 4 shows the advantageous synthetic approach of thepresent disclosure, whereby a sulfonated iminodiacetic acid can beproduced in conjunction with ammonium ions (not shown) through reactingiminodiacetonitrile with a sultone under acidic conditions, wherein A is(CH₂)_(x) and x is 2, 3 or 4.

Under the acidic reaction conditions, the initially produced sulfonatediminodiacetonitrile undergoes hydrolysis to the corresponding sulfonatediminodiacetic acid with the concurrent production of ammonium ions.Although the sulfonated iminodiacetonitrile intermediate could, inprinciple, be isolated, it can more desirably be hydrolyzed in situ suchthat the sulfonated iminodiacetic acid is formed in a single pot fromthe iminodiacetonitrile. The particular example utilizing 1,3-propanesultone as the reaction partner for iminodiacetonitrile is shown inReaction 5.

In addition to the ability to form sulfonated iminodialkanoic acids inthe absence of alkali metal ions, advantages of the synthetic approachesexemplified in Reactions 2-5 include the benefit that the sulfonatediminodiacetic acids form in near-quantitative yields as a concentrate inan aqueous reaction medium. The concentrate may be used directly in anacidizing operation or undergo dilution with a carrier fluid in thecourse of formulating an acidizing fluid. Accordingly, in someembodiments, treatment fluids of the present disclosure may beformulated or produced such that they are substantially free of alkalimetal ions. As used herein, the term “substantially free of alkali metalions” refers to an alkali metal content of about 5 wt. % or less,particularly an alkali metal content of about 1 wt. % or less.

Accordingly, in various embodiments, certain methods of the presentdisclosure can comprise reacting an iminodialkylnitrile with a sultoneunder acidic conditions to form a fluid comprising a sulfonatediminodialkanoic acid and ammonium ions. Such synthetic methods areexemplified by Reactions 4 and 5 above, and illustrative sulfonatediminodialkanoic acids of this type are shown in Formulas 1-3 above. Inmore particular embodiments, the iminodialkanoic acid can have astructure corresponding to Formula 3, in which x is an integer rangingbetween 1 and about 6, or 2, 3, or 4, in particular. Accordingly, insuch embodiments, the methods can include reacting iminodiacetonitrilewith a sultone that can be ethane sultone, 1,3-propane sultone, or1,4-butane sultone.

In illustrative embodiments, the acidic conditions under which theiminodialkanoic acid is synthesized can comprise an aqueous solutionhaving a pH of about 2 or less and containing the iminodialkylnitrileand the sultone. Any suitable acid can be used to produce the acidicconditions in the aqueous solution. Illustrative acids that can besuitable in this regard include mineral and organic acids such as, forexample, hydrochloric acid, hydrobromic acid, hydrofluoric acid, formicacid, acetic acid, chloroacetic acid, dichloroacetic acid,trichloroacetic acid, methanesulfonic acid, citric acid, maleic acid,glycolic acid, lactic acid, malic acid, oxalic acid, the like, and anycombination thereof. Hydrofluoric acid can be present when the treatmentfluids are used to affect dissolution of siliceous materials, asdiscussed further herein.

In some embodiments, the iminoalkylnitrile can be reacted with thesultone under the acidic conditions at a temperature of about 80° C. orless. Lower reaction temperatures can help preclude unwanted expulsionof ammonia from the reaction mixture. In other illustrative embodiments,the reaction to form the sulfonated iminodialkanoic acid may occur at atemperature ranging between about 50° C. and about 100° C., or betweenabout 60° C. and about 80° C.

In other various embodiments, certain methods for synthesizing asulfonated iminodialkanoic acid can comprise reacting an iminodialkanoicacid with a sultone under acidic conditions to form a fluid comprising asulfonated iminodialkanoic acid. Such synthesis methods are exemplifiedby Reactions 2 and 3 above, which are differentiated from Reactions 4and 5 in that they do not produce ammonium ions in situ. Illustrativereaction conditions for forming sulfonated iminodialkanoic acids in thismanner are similar to those provided above an iminodialkylnitrile as astarting material.

Accordingly, in some embodiments, the present disclosure providestreatment fluids comprising an aqueous carrier fluid having an acidicpH, a sulfonated iminodialkanoic acid, and ammonium ions. In someembodiments, the sulfonated iminodialkanoic acid can be in its fullyprotonated form. In other embodiments, the sulfonated iminodialkanoicacid can be at least partially deprotonated in the acidic aqueoussolution, in which case the ammonium ions can serve as a counterion toprovide charge balance. The presence of ammonium ions can beadvantageous for the reasons discussed above.

Aqueous carrier fluids used for forming the treatment fluids of thepresent disclosure may be obtained from any suitable source. In someembodiments, suitable aqueous carrier fluids may include, for example,fresh water, acidified water, treated water, salt water, seawater,brackish water, produced water, flowback water, brine (e.g., a saturatedsalt solution), or an aqueous salt solution (e.g., a non-saturated saltsolution). When it is desired for the treatment fluids to besubstantially free of alkali metal ions, certain aqueous carrier fluids(e.g., salt water, seawater, brine, aqueous salt water, and the like)may not be suitable, unless they have undergone a treatment to remove asubstantial portion of their alkali metal ions.

In further embodiments, an organic co-solvent may be present in thetreatment fluids in combination with the aqueous carrier fluid. Suitableorganic co-solvents may include, but are not limited to, glycols andalcohol solvents, for example. When present, an amount of the organicco-solvent may range between about 1% to about 50% by volume of thetreatment fluid.

In various embodiments, the treatment fluid may have a pH of about 4 orless, or a pH of about 3 or less, or a pH of about 2 or less, or a pH ofabout 1 or less. If the pH of the concentrate or a combination of theconcentrate and a carrier fluid is not in a desired range, the methodsdescribed herein may further comprise raising the pH of the treatmentfluid with a base prior use of the treatment fluid in a subterraneanformation. In some embodiments, ammonium hydroxide may comprise asuitable base for raising the pH, particularly if the treatment fluid isto be maintained in a form that is substantially free of alkali metalions. Amine bases may also be suitable in this regard. Alkali metalbases may be suitable if there is no need to maintain the treatmentfluids free of alkali metal ions. Acids or acid-generating compounds maybe used similarly to lower the pH, if desired.

In some embodiments, the treatment fluids containing the sulfonatediminodialkanoic acid may further comprise an acid or an acid-generatingcompound. The acid or acid-generating compound may supplement the innateacidity of the sulfonated iminodialkanoic acid so that the treatmentfluid spends less quickly. Both organic acids and mineral acids may beused for this purpose. Examples of organic and mineral acids that may besuitable in this regard include, for example, hydrochloric acid,hydrobromic acid, hydrofluoric acid, formic acid, acetic acid,chloroacetic acid, dichloroacetic acid, trichloroacetic acid,methanesulfonic acid, citric acid, maleic acid, glycolic acid, lacticacid, malic acid, oxalic acid, gluconic acid, succinic acid, tartaricacid, sulfamic acid, the like, and any combination thereof. It may beparticularly desirable to include hydrofluoric acid in the treatmentfluids when acidizing a subterranean formation comprising a siliceousmineral or a subterranean formation of mixed mineralogy comprising botha siliceous mineral and a carbonate mineral.

Suitable acid-generating compounds can include, for example, esters,aliphatic polyesters, orthoesters, poly(orthoesters), poly(lactides),poly(glycolides), poly(ε-caprolactones), poly(hydroxybutyrates),poly(anhydrides), ethylene glycol monoformate, ethylene glycoldiformate, diethylene glycol diformate, glyceryl monoformate, glyceryldiformate, glyceryl triformate, triethylene glycol diformate, formateesters of pentaerythritol, the like, any derivative thereof, and anycombination thereof.

In some embodiments, treatment fluids of the present disclosure mayfurther comprise hydrofluoric acid or a hydrofluoric acid-generatingcompound. Suitable hydrofluoric acid-generating compounds may includesubstances such as, for example, fluoroboric acid, fluorosulfuric acid,hexafluorophosphoric acid, hexafluoroantimonic acid, difluorophosphoricacid, hexafluorosilicic acid, potassium hydrogen difluoride, sodiumhydrogen difluoride, polyvinylammonium fluoride, polyvinylpyridiniumfluoride, pyridinium fluoride, imidazolium fluoride, ammonium fluoride,tetrafluoroborate salts, hexafluoroantimonate salts, hexafluorophosphatesalts, bifluoride salts (e.g., ammonium bifluoride), perfluorinatedorganic compounds, boron trifluoride and various boron trifluoridecomplexes.

When used, a hydrofluoric acid-generating compound can be present in thetreatment fluids described herein in an amount ranging between about0.1% to about 20% by weight of the treatment fluid. In otherembodiments, an amount of the hydrofluoric acid-generating compound canrange between about 0.5% to about 10% by weight of the treatment fluidor between about 0.5% to about 8% by weight of the treatment fluid.Hydrofluoric acid, when present, may be used in similar concentrationranges.

In further embodiments, the treatment fluids described herein mayfurther comprise any number of additives that are commonly used indownhole operations including, for example, silica scale controladditives, corrosion inhibitors, surfactants, gel stabilizers,anti-oxidants, polymer degradation prevention additives, relativepermeability modifiers, scale inhibitors, foaming agents, defoamingagents, antifoaming agents, emulsifying agents, de-emulsifying agents,iron control agents, proppants or other particulates, particulatediverters, acids, fluid loss control additives, gas, catalysts, claycontrol agents, dispersants, flocculants, scavengers (e.g., H₂Sscavengers, CO₂ scavengers or O₂ scavengers), gelling agents,lubricants, friction reducers, bridging agents, viscosifiers, weightingagents, solubilizers, pH control agents (e.g., buffers), hydrateinhibitors, consolidating agents, bactericides, catalysts, claystabilizers, breakers, delayed release breakers, and the like. Anycombination of these additives may be used as well. One of ordinaryskill in the art will be able to formulate a treatment fluid havingproperties suitable for a given application.

In other various embodiments, methods for treating a subterraneanformation are described herein. In some embodiments, the methods maycomprise: providing a treatment fluid comprising an aqueous carrierfluid having an acidic pH, a sulfonated iminodialkanoic acid, andammonium ions; introducing the treatment fluid into a subterraneanformation; and complexing one or more metal ions in the subterraneanformation with the sulfonated iminodialkanoic acid. In additionalembodiments, the methods may further comprise dissolving anacid-reactive substance in the subterranean formation with the treatmentfluid to generate the one or more metal ions. In various embodiments,the acid-reactive substance may comprise a carbonate material or asiliceous material, as discussed further herein.

In further embodiments, providing the treatment fluid may comprisereacting an iminodialkylnitrile with a sultone under acidic conditionsin an aqueous solution to form the sulfonated iminodialkanoic acid. Insuch embodiments, the treatment fluid can be substantially free ofalkali metal ions and the ammonium ions can be formed in situ. Thesulfonated iminodialkanoic acid may be formed in a concentrate having anacidic pH, which may be used directly as a treatment fluid in anacidizing operation or after undergoing additional dilution with acarrier fluid.

In alternative embodiments, providing the treatment fluid may comprisereacting an iminodialkanoic acid with a sultone under acidic conditionsin an aqueous solution to form the sulfonated iminodialkanoic acid. Insuch embodiments, a source of ammonium ions, such as ammonium hydroxideor ammonium chloride, may be added to the aqueous solution after formingthe sulfonated iminodialkanoic acid.

In more specific embodiments, providing the treatment fluid may comprisereacting iminodiacetonitrile with 1,3-propane sultone in an aqueoussolution under acidic conditions to form a concentrate comprising asulfonated iminodiacetic acid, and optionally, diluting the concentratewith a carrier fluid.

In some embodiments, the concentrate obtained from the reaction to formthe sulfonated iminodialkanoic acid may be used directly in a treatmentoperation without further dilution. In such embodiments, a concentrationof the sulfonated iminodialkanoic acid in the treatment fluid and in theconcentrate may range between about 0.1 M to about 5 M. In moreparticular embodiments, the concentration may range between about 0.5 Mand about 5 M, or between about 1 M and about 5 M, or between about 2 Mand about 5 M, or between about 2 M and about 4 M. Dilution of theconcentrate with a carrier fluid may be used to lower the concentrationof the sulfonated iminodialkanoic acid to a suitable working range,which may include a range between about 0.01 M and about 4 M in someembodiments.

In other more specific embodiments, methods of the present disclosuremay comprise: providing a treatment fluid comprising an aqueous carrierfluid having an acidic pH, a sulfonated iminodialkanoic acid, andammonium ions; introducing the treatment fluid into a subterraneanformation; at least partially dissolving an acid-reactive substance inthe subterranean formation in the presence of the sulfonatediminodialkanoic acid to generate one or more metal ions; and complexingthe one or more metal ions in the subterranean formation with thesulfonated iminodialkanoic acid.

In the methods of the present disclosure, a sulfonated iminodialkanoicacid may complex one or more metal ions in order to mitigate the metalions' ability to undergo secondary reactions and form a precipitatewithin the subterranean formation. The resulting metal complexes mayremain within the subterranean formation, or they may be producedtherefrom before or concurrent with production of a hydrocarbonresource. In some embodiments, the metal complexes may remain solublewithin the treatment fluid. In some embodiments, complexation of metalions may, at least in part, promote dissolution of an acid-reactivesubstance by the sulfonated iminodialkanoic acids described herein.

In other embodiments, acidity of sulfonated iminodialkanoic acids maydirectly promote dissolution of an acid-reactive substance withoutcomplexation taking place. As indicated above, the sulfonatediminodialkanoic acids described herein are highly acidic substances bythemselves, and in addition to their metal complexation properties, theymay also promote dissolution of an acid-reactive substance containingmetal ions through their acidity. Accordingly, in some embodiments, thesulfonated iminodialkanoic acid may be present alone in a treatmentfluid, such that the treatment fluid is free of mineral acids and otherorganic acids. In some embodiments, the sulfonated iminodialkanoic acidmay serve as a replacement for a mineral acid, such as hydrochloricacid, in a treatment fluid. This may particularly be the case when thetreatment fluids of the present disclosure are used for acidizing asubterranean formation that primarily comprises a carbonate mineral suchas calcite, dolomite, or the like.

In some embodiments, however, treatment fluids comprising a sulfonatediminodialkanoic acid and ammonium ions may further comprise an acid oran acid-generating compound. Suitable acids and acid-generatingcompounds that may be present are described above. The acid oracid-generating compound may supplement the innate acidity of thesulfonated iminodialkanoic acid so that the treatment fluid spends lessquickly.

In more particular embodiments, the acid-reactive substance may comprisea carbonate mineral. Carbonate minerals that may undergo dissolution inthe presence of the treatment fluids of the present disclosure include,for example, calcite (calcium carbonate), dolomite (calcium magnesiumcarbonate), siderite (iron carbonate), or any combination thereof.Particularly when acidizing a calcite or dolomite formation, the one ormore metal ions that are complexed by the chelating agent may compriseat least calcium ions. When acidizing a subterranean formationcomprising siderite, the one or more metal ions undergoing complexationby the chelating agent may comprise iron ions and iron control may beachieved. In either case, by complexing the metal ions with thesulfonated iminodialkanoic acid, the solubility limit of the metal ionsmay be increased relative to the uncomplexed form, thereby lessening thelikelihood of damaging precipitates forming within the subterraneanformation.

In more specific embodiments, metal ions that may be complexed by thesulfonated iminodialkanoic acid include alkaline earth metal ions,transition metal ions, main group metal ions, lanthanide ions, or anycombination thereof. In more particular embodiments, metal ions that maybe complexed by the sulfonated iminodialkanoic acids include calciumions, iron ions, aluminum ions, or any combination thereof. Zinc ions,titanium ions, and/or zirconium ions may also be desirable to complexfor similar reasons. By complexing these metal ions and others, it maybe possible to preclude their formation of damaging scale orparticipating in secondary precipitation reactions in a subterraneanformation.

In other more particular embodiments, the acid-reactive substance maycomprise a siliceous material, which optionally may be present incombination with a carbonate material. When a siliceous material ispresent, dissolution of the siliceous material may be promoted byhydrofluoric acid or a hydrofluoric acid-generating compound. Thehydrofluoric acid or hydrofluoric acid-generating compound may bepresent in the treatment fluid or introduced to the subterraneanformation separately from the sulfonated iminoalkanoic acid. Bycomplexing metal ions that may be present in the subterranean formation,the metal ions may be prevented from undergoing secondary reactions withdissolved silicon compounds or with the hydrofluoric acid itself. Forexample, by complexing calcium ions, the calcium ions may be preventedfrom undergoing a secondary reaction to form damaging calcium fluorideprecipitates. Accordingly, in some embodiments, the treatment fluidsdescribed herein may be used to complex metal ions when dissolving asiliceous material also containing a carbonate material therein. Doingso can allow metal ions from the carbonate material to undergosequestration so that they do not interfere with the hydrofluoric acidused for dissolution of the siliceous material.

When hydrofluoric acid or a hydrofluoric acid-generating compound isused to promote dissolution of a siliceous material, the hydrofluoricacid or the hydrofluoric acid-generating compound may be present in thetreatment fluid comprising the sulfonated iminodialkanoic acid or it maybe introduced in a separate treatment fluid. When introduced to thesubterranean formation in a separate treatment fluid, the treatmentfluid comprising the sulfonated iminodialkanoic acid may be introducedto the subterranean formation first in order to promote metal ioncomplexation before forming dissolved silicon compounds from thesiliceous mineral. Alternatively, the treatment fluid comprising thesulfonated iminodialkanoic acid may pre-condition the subterraneanformation before dissolved silicon is formed therein.

As indicated above, when a siliceous material is being dissolved by thetreatment fluids of the present disclosure, the treatment fluid candesirably be substantially free of alkali metal ions in variousembodiments.

In some embodiments, the treatment fluids described herein may be usedin treating a particulate pack in a subterranean formation. Particulatepacks may include, for example, proppant packs and gravel packs.Treatment of a particulate pack may beneficially allow the permeabilityof the pack to be increased, such that it presents a lower impediment tofluid flow.

In some embodiments, the treatment fluids described herein may beutilized in matrix acidizing operations. That is, in some embodiments,the treatment fluids described herein can be introduced to asubterranean formation below a fracture gradient pressure of thesubterranean formation. In some embodiments, the interaction of thetreatment fluid with the formation matrix may result in the desirableformation of wormholes therein. In other embodiments, the treatmentfluids described herein can be introduced to a subterranean formation ator above a fracture gradient pressure of the subterranean formation,such that one or more fractures are created or enhanced in thesubterranean formation. Given the benefit of the present disclosure andthe understanding of one having ordinary skill in the art, one canreadily determine whether to introduce the treatment fluids to asubterranean formation at matrix flow rates (i.e., below the fracturegradient pressure) or at fracturing flow rates (i.e., at or above thefracture gradient pressure).

In some or other embodiments, the treatment fluids described herein maybe used in remediation operations within a subterranean formation.Specifically, in some embodiments, treatment fluids described hereincomprising a sulfonated iminodialkanoic acid may be used to removeprecipitation or accumulation damage within a subterranean formation. Asused herein, the term “precipitation or accumulation damage” refers to asiliceous or non-siliceous scale that has been dissolved in asubterranean formation and deposited elsewhere within the subterraneanformation.

In some embodiments, the treatment fluids described herein may be usedin conjunction with drilling a wellbore penetrating a subterraneanformation. For example, when used during drilling, the treatment fluidsmay desirably leave the subterranean formation conditioned with thechelating agent so that precipitation can be subsequently mitigated at alater time.

In still other various embodiments, systems configured for delivering atreatment fluid of the present disclosure to a downhole location aredescribed herein. In various embodiments, the systems can comprise apump fluidly coupled to a tubular, the tubular containing a treatmentfluid that comprises an aqueous carrier fluid having an acidic pH, asulfonated iminodialkanoic acid, and ammonium ions. In more particularembodiments, the iminodialkanoic acid can be substantially free ofalkali metal ions and have a structure exemplified by Formula 3, inwhich x is 2, 3, or 4.

The pump may be a high pressure pump in some embodiments. As usedherein, the term “high pressure pump” will refer to a pump that iscapable of delivering a fluid downhole at a pressure of about 1000 psior greater. A high pressure pump may be used when it is desired tointroduce a treatment fluid of the present disclosure to a subterraneanformation at or above a fracture gradient of the subterranean formation,but it may also be used in cases where fracturing is not desired. Thetreatment fluids described herein may be introduced with a high pressurepump, or they may be introduced following a treatment fluid (e.g., a padfluid) that was introduced with a high pressure pump. In someembodiments, the high pressure pump may be capable of fluidly conveyingparticulate matter into the subterranean formation. Suitable highpressure pumps will be known to one having ordinary skill in the art andmay include, but are not limited to, floating piston pumps and positivedisplacement pumps.

In other embodiments, the pump may be a low pressure pump. As usedherein, the term “low pressure pump” will refer to a pump that operatesat a pressure of about 1000 psi or less. In some embodiments, a lowpressure pump may be fluidly coupled to a high pressure pump that isfluidly coupled to the tubular. That is, in such embodiments, the lowpressure pump may be configured to convey the treatment fluid to thehigh pressure pump. In such embodiments, the low pressure pump may “stepup” the pressure of a treatment fluid before it reaches the highpressure pump.

In some embodiments, the systems described herein can further comprise amixing tank that is upstream of the pump and in which the sulfonatediminodialkanoic acid is provided in a concentrate and/or combined with acarrier fluid. Formation of the sulfonated iminodialkanoic acid may alsooccur in the mixing tank, in some embodiments. In various embodiments,the pump (e.g., a low pressure pump, a high pressure pump, or acombination thereof) may convey the treatment fluid from the mixing tankor other source of the treatment fluid to the tubular. In otherembodiments, however, the treatment fluid can be formulated offsite andtransported to a worksite, in which case the treatment fluid may beintroduced to the tubular via the pump directly from its shippingcontainer (e.g., a truck, a railcar, a barge, or the like) or from atransport pipeline. In either case, the treatment fluid may be drawninto the pump, elevated to an appropriate pressure, and then introducedinto the tubular for delivery downhole.

FIG. 1 shows an illustrative schematic of a system that can delivertreatment fluids of the present disclosure to a downhole location,according to one or more embodiments. It should be noted that while FIG.1 generally depicts a land-based system, it is to be recognized thatlike systems may be operated in subsea locations as well. As depicted inFIG. 1, system 1 may include mixing tank 10, in which a treatment fluidof the present disclosure may be formulated. The treatment fluid may beconveyed via line 12 to wellhead 14, where the treatment fluid enterstubular 16, tubular 16 extending from wellhead 14 into subterraneanformation 18. Tubular 16 may include orifices that allow the treatmentfluid to enter into the wellbore. Pump 20 may be configured to raise thepressure of the treatment fluid to a desired degree before itsintroduction into tubular 16. It is to be recognized that system 1 ismerely exemplary in nature and various additional components may bepresent that have not necessarily been depicted in FIG. 1 in theinterest of clarity. Non-limiting additional components that may bepresent include, but are not limited to, supply hoppers, valves,condensers, adapters, joints, gauges, sensors, compressors, pressurecontrollers, pressure sensors, flow rate controllers, flow rate sensors,temperature sensors, and the like.

Although not depicted in FIG. 1, the treatment fluid may, in someembodiments, flow back to wellhead 14 and exit subterranean formation18. Flowback of the treatment fluid may serve to remove complexed metalions from the subterranean formation, for example. In some embodiments,the treatment fluid that has flowed back to wellhead 14 may subsequentlybe recovered and recirculated to subterranean formation 18. In otherembodiments, the treatment fluid may flow back to wellhead 14 in aproduced hydrocarbon fluid from subterranean formation 18.

It is also to be recognized that the disclosed treatment fluids may alsodirectly or indirectly affect the various downhole equipment and toolsthat may come into contact with the fracturing fluids during operation.Such equipment and tools may include, but are not limited to, wellborecasing, wellbore liner, completion string, insert strings, drill string,coiled tubing, slickline, wireline, drill pipe, drill collars, mudmotors, downhole motors and/or pumps, surface-mounted motors and/orpumps, centralizers, turbolizers, scratchers, floats (e.g., shoes,collars, valves, etc.), logging tools and related telemetry equipment,actuators (e.g., electromechanical devices, hydromechanical devices,etc.), sliding sleeves, production sleeves, plugs, screens, filters,flow control devices (e.g., inflow control devices, autonomous inflowcontrol devices, outflow control devices, etc.), couplings (e.g.,electro-hydraulic wet connect, dry connect, inductive coupler, etc.),control lines (e.g., electrical, fiber optic, hydraulic, etc.),surveillance lines, drill bits and reamers, sensors or distributedsensors, downhole heat exchangers, valves and corresponding actuationdevices, tool seals, packers, cement plugs, bridge plugs, and otherwellbore isolation devices, or components, and the like. Any of thesecomponents may be included in the systems generally described above anddepicted in FIG. 1.

Embodiments disclosed herein include:

A. Methods for synthesizing a sulfonated iminodialkanoic acid. Themethods comprise: reacting an iminodialkylnitrile with a sultone underacidic conditions to form a fluid comprising a sulfonatediminodialkanoic acid and ammonium ions.

B. Treatment fluids comprising a sulfonated iminodialkanoic acid. Thetreatment fluids comprise: an aqueous carrier fluid having an acidic pH;a sulfonated iminodialkanoic acid; and ammonium ions.

C. Systems incorporating a treatment fluid comprising a sulfonatediminodialkanoic acid. The systems comprise: a pump fluidly coupled to atubular, the tubular containing a treatment fluid comprising an aqueouscarrier fluid having an acidic pH, a sulfonated iminodialkanoic acid,and ammonium ions.

D. Methods for treating a subterranean formation. The methods comprise:providing a treatment fluid comprising an aqueous carrier fluid havingan acidic pH, a sulfonated iminodialkanoic acid, and ammonium ions;introducing the treatment fluid into a subterranean formation; andcomplexing one or more metal ions in the subterranean formation with thesulfonated iminodialkanoic acid.

E. Methods for treating a subterranean formation. The methods comprise:providing a treatment fluid comprising an aqueous carrier fluid havingan acidic pH, a sulfonated iminodialkanoic acid, and ammonium ions;introducing the treatment fluid into a subterranean formation; at leastpartially dissolving an acid-reactive substance in the subterraneanformation in the presence of the sulfonated iminodialkanoic acid togenerate one or more metal ions; and complexing the one or more metalions in the subterranean formation with the sulfonated iminodialkanoicacid.

Each of embodiments A-E may have one or more of the following additionalelements in any combination:

Element 1: wherein the sulfonated iminodialkanoic acid has a structureof

wherein x is an integer ranging between 1 and about 6.

Element 2: wherein x is 2, 3 or 4.

Element 3: wherein the iminodialkylnitrile is iminodiacetonitrile andthe sultone is 1,3-propanesultone.

Element 4: wherein the acidic conditions are present in an aqueoussolution comprising the iminodialkylnitrile and the sultone, the aqueoussolution having a pH of about 2 or less.

Element 5: wherein the iminodialkylnitrile is reacted with the sultonein the aqueous solution at a temperature of about 80° C. or less.

Element 6: wherein the fluid is substantially free of alkali metal ions.

Element 7: wherein the treatment fluid has a pH of about 2 or less.

Element 8: wherein the treatment fluid further comprises hydrofluoricacid or a hydrofluoric acid-generating compound.

Element 9: wherein the treatment fluid is prepared by reacting animinodialkylnitrile with a sultone under acidic conditions in an aqueoussolution to form the sulfonated iminodialkanoic acid.

Element 10: wherein the method further comprises: dissolving anacid-reactive substance in the subterranean formation with the treatmentfluid to generate the one or more metal ions.

Element 11: wherein the acid-reactive substance comprises a siliceousmaterial.

Element 12: wherein the acid-reactive substance comprises a carbonatematerial.

Element 13: wherein providing the treatment fluid comprises: reacting animinodialkylnitrile with a sultone under acidic conditions in an aqueoussolution to form the sulfonated iminodialkanoic acid.

By way of non-limiting example, exemplary combinations applicable to A-Einclude:

The method of A, the treatment fluid of B, or the system of C incombination with elements 1 and 2; 1 and 4; 3 and 4; 1 and 5; 3 and 5; 1and 6; 3 and 6; 1 and 7; 3 and 7; 6 and 7; 1 and 8; 3 and 8; 6 and 8; or7 and 8.

The method of D in combination with elements 1 and 2; 1 and 6; 3 and 6;1 and 7; 3 and 7; 6 and 7; 1 and 8; 3 and 8; 6 and 8; 7 and 8; 10 and11; 10 and 12; 8, 10 and 11; 1, 10 and 11; 1, 10 and 12; 3 and 10; 6, 8,10 and 11; or 7 and 13.

The method of E in combination with elements 1 and 2; 1 and 6; 3 and 6;1 and 7; 3 and 7; 6 and 7; 1 and 8; 3 and 8; 6 and 8; 7 and 8; 8 and 11;1 and 11; 1 and 12; 3 and 12; 7 and 10; 7 and 11; 6, 8 and 11; 7 and 13;or 3 and 11.

To facilitate a better understanding of the embodiments of the presentdisclosure, the following examples of preferred or representativeembodiments are given. In no way should the following examples be readto limit, or to define, the scope of the disclosure.

EXAMPLES Example 1: Synthesis of a Sulfonated Iminodiacetic Acid fromIminodiacetic Acid

The sulfonated iminodiacetic acid was synthesized as generally shown inReaction 2 above. 15.5 g of iminodiacetic acid (116 mmol) and 14.2 g of1,2-oxathiolane 2,2-dioxide (116 mmol) were combined in 35 mL water. Thereaction mixture was stirred at 85° C. for 4 hours, and reactionprogress was monitored by NMR until the resonances of the startingmaterials disappeared. The resulting aqueous solution was used withoutpurification or further manipulation.

Example 2: Synthesis of a Sulfonated Iminodiacetic Acid fromIminodiacetonitrile

A 125 mL roundbottom pressure flask equipped with a magnetic stirrer wascharged with 30 mL of water, 11.16 g of iminodiacetonitrile (116 mmol)and 14.2 g of 1,2-oxathiolane 2,2-dioxide (116 mmol). The temperaturewas raised to 85° C., and the reaction mixture became homogenous afterabout 5 minutes at that temperature. To the homogenous reaction mixturewas then added 58 mmol of sulfuric acid to promote nitrile hydrolysisduring the remaining reaction time.

Example 3: Effects of a Sulfonated Iminodiacetic Acid on CalciumDissolution

An aliquot of the reaction mixture from Example 1 was diluted to avolume of 10 mL and a concentration of 0.6 M, and the pH was adjusted toapproximately 1. Thereafter, varying amounts of CaCl₂ solution and 50%NaOH solution were added to the pH-adjusted aliquot. FIG. 2 shows a bargraph summarizing the amounts of CaCl₂ and NaOH added to the chelantsolution of Example 1 and the resulting pH values. No precipitateformation occurred in any of the tested configurations, even at pHvalues and calcium concentrations where calcium hydroxide precipitationwould normally be expected to occur.

Example 4: Stabilization of Calcium Ions in the Presence of HydrofluoricAcid

A control solution was prepared by dissolving CaCl₂ and ammoniumbifluoride each at a concentration of 0.6 M in 5 mL of water. A testsolution was prepared in the same manner as the control solution, exceptan equivalent molar amount of the chelating agent of Example 1 was addedto this solution. The pH value of the control solution was raised toabout 7 and the pH value of the test solution was raised to about 4 byadding ammonium hydroxide. Within about 5 minutes, a thick precipitatehad formed and settled in the control solution. In contrast, in the testsolution, a milky suspension formed, and it did not settle upon standingfor 24 hours.

Example 5: Acidizing of a Calcite Core

The chelant solution of Example 1 was contacted with a calcite core, andthe core's differential pressure and permeability were monitored overtime. FIG. 3 shows a plot of differential pressure and permeability fora calcite core contacted with the chelant solution of Example 1 as afunction of time. As shown in FIG. 3, a significant drop in differentialpressure and an increase in permeability of the core occurred after acontact time period. Thus, it can be concluded that the sulfonatediminodiacetic acid alone was effective to promote dissolution of thecalcium carbonate in the core.

Unless otherwise indicated, all numbers expressing quantities ofingredients, properties such as molecular weight, reaction conditions,and so forth used in the present specification and associated claims areto be understood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the specification and attached claims are approximationsthat may vary depending upon the desired properties sought to beobtained by the embodiments of the present disclosure. At the veryleast, and not as an attempt to limit the application of the doctrine ofequivalents to the scope of the claim, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

Therefore, the present disclosure is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent disclosure may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered,combined, or modified and all such variations are considered within thescope and spirit of the present disclosure. The disclosureillustratively disclosed herein suitably may be practiced in the absenceof any element that is not specifically disclosed herein and/or anyoptional element disclosed herein. While compositions and methods aredescribed in terms of “comprising,” “containing,” or “including” variouscomponents or steps, the compositions and methods can also “consistessentially of” or “consist of” the various components and steps. Allnumbers and ranges disclosed above may vary by some amount. Whenever anumerical range with a lower limit and an upper limit is disclosed, anynumber and any included range falling within the range are specificallydisclosed. In particular, every range of values (of the form, “fromabout a to about b,” or, equivalently, “from approximately a to b,” or,equivalently, “from approximately a-b”) disclosed herein is to beunderstood to set forth every number and range encompassed within thebroader range of values. Also, the terms in the claims have their plain,ordinary meaning unless otherwise explicitly and clearly defined by thepatentee. Moreover, the indefinite articles “a” or “an,” as used in theclaims, are defined herein to mean one or more than one of the elementthat it introduces.

The invention claimed is:
 1. A method comprising: reacting animinodialkylnitrile with a sultone under acidic conditions to form afluid comprising a sulfonated iminodialkanoic acid and ammonium ions. 2.The method of claim 1, wherein the sulfonated iminodialkanoic acid has astructure of

wherein x is an integer ranging between 1 and about
 6. 3. The method ofclaim 1, wherein the iminodialkylnitrile is iminodiacetonitrile and thesultone is 1,3-propanesultone and wherein the acidic conditions arepresent in an aqueous solution comprising the iminodialkylnitrile andthe sultone, the aqueous solution having a pH of about 2 or less.
 4. Themethod of claim 3, wherein the iminodialkylnitrile is reacted with thesultone in the aqueous solution at a temperature of about 80° C. orless.
 5. The method of claim 1, wherein the fluid is substantially freeof alkali metal ions.